1. Field of the Invention
The present invention relates to a sheet tray of an image forming apparatus, and particularly to a sheet tray of an image forming apparatus which is disposed at a sheet feed part or sheet discharge part of the image forming apparatus and is provided with a second tray angularly displaceably supported at an end to a body of the sheet tray and foldable onto an upper surface side thereof.
2. Description of Related Art
Conventionally, as described in Japanese Unexamined Patent Publication JP-A 5-319635 (1993), there has been known a sheet feed tray having such a constitution that a second tray is attached to a sheet tray body angularly displaceably about a supporting shaft so as to be foldable onto an upper surface side thereof and when the second tray is angularly displaced, the second tray abuts against a portion of the sheet tray body which is outside the supporting shaft of the sheet tray body so that he second tray is stopped in the sheet stacking position.
The sheet feed tray is used in such a way that when the size of sheets to be stacked in the sheet feed tray is small, this sheet feed tray is used in the state that the second tray is folded on the upper surface side of the sheet tray body, while when the size of the sheets stacked in the tray is large, the sheet feed tray is used in the state that the second tray is unfolded.
In the sheet feed tray of the image forming apparatus having such a constitution, assuming that the sheet feed tray is used in the state that the second tray is unfolded, when a load which exceeds the maximum loading weight of the second tray is applied to the second tray, an excessive force is applied to the supporting shaft which angularly displaceably supports the second tray or to the sheet feed tray itself and hence, there arises a problem that a damage of this supporting shaft or sheet feed tray occurs.
A sheet tray of an image forming apparatus of the invention has been made to solve the above-mentioned problem and it is an object of the invention to prevent a sheet tray or the like from being damaged by providing the sheet tray with a second tray supported on a body thereof so that the second tray is angularly displaceable in the downward direction from sheet stacking position when a load which exceeds a maximum loading weight is applied to the second tray.
To achieve the above-mentioned object, there is provided a sheet tray for an image forming apparatus, which is disposed at a sheet feed part or sheet discharge part of the image forming apparatus, the sheet tray comprising:
a body;
a second tray angularly displaceably supported on an end of the body of the sheet tray, the second tray being fordable onto an upper surface side of the sheet tray body, wherein the second tray is arranged to be angularly displaceable downwardly from a sheet stacking position when a force which exceeds a maximum loading weight of the second tray is applied to the sheet tray.
According to such a constitution, when the load which exceeds the maximum loading weight of the second tray is applied to the second tray, the second tray is angularly displaced downwardly whereby a supporting portion of the sheet tray which angularly displaceably supports the second tray can be prevented from being damaged.
In the invention it is preferable that the sheet tray comprises a stopper member for holding the second tray at a sheet stacking position and at a downwardly displaced position by abutting the second tray against the stopper member.
According to the invention, when the second tray which is held in the sheet stacking position by the stopper member is displaced downwardly upon receiving a force which exceeds a maximum loading weight of the second tray, the stopper holds the second tray at a downwardly displaced position, so that the second tray can be prevented from being angularly displaced excessively whereby the second tray can be surely prevented from being diamaged.
Further, in the invention it is preferable that a resiliency of the stopper member is set greater than that of the second tray.
According to the invention, when a load of a stack of sheets exceeding the maximum loading weight of the second tray is applied to the second tray, the stopper member is deformed by the weight applied to the second tray and hence, the second tray is displaced downwardly. Accordingly, the stack of sheets drop from the sheet tray, so that the sheet tray can be prevented from being damaged.
That is, when the second tray is displaced downwardly upon application of a force which exceeds the maximum loading weight to the second tray, the stopper member is deformed due to its own resiliency, which makes it possible to angularly displace the second tray downwardly. In this case, since the stopper member has a resiliency greater than that of the second tray, the second tray is not deformed and hence is angularly displaced while holding its flatness, so that the second tray can be prevented from being damaged.
Further, in the invention it is preferable that the stopper member is elastically deformed depending on a distance from the supported portion of the second tray on the end of the body of the sheet tray to the stopper member.
Accordingly, by merely changing the distance from the supported portion of the second tray to the stopper member, the maximum loading weight of the second tray can be varied. For example, when the distance from the supported portion of the second tray is made short, in angularly displacing the second tray downwardly from the sheet stacking position, unless the stopper member is deformed largely, the second tray cannot be displaced downwardly from the sheet stacking position. Accordingly, even when a large force is applied to the second tray, the second tray is held in the sheet stacking position and hence, the maximum loading weight can be increased.
Further, in the invention it is preferable that the stopper member is integrally formed with the sheet tray body and the thickness of the stopper member is made thinner than that of the sheet tray body.
In this manner, since the thickness of the stopper member is thinner than that of the sheet tray body, there is no possibility that due to the deformation of the stopper member generated at the time of angularly displacing the second tray, the force applied to the second tray will affect the sheet tray body. Accordingly, with such a simple constitution the sheet tray body can be prevented from being damaged. That is, the sheet tray body can maintain the flatness without being deflected and hence, the sheet tray body can be prevented from being damaged.
Further, in the invention it is preferable that a point where a supporting side end of the second tray abuts against the stopper in the sheet stacking position is set below a crossing point where a central line of the second tray and the stopper member cross perpendicular to each other and corresponds to the maximum loading weight.
Accordingly, when a load of a stack of sheets exceeding the maximum loading weight is applied to the second tray, the stopper member is deformed due to the load applied to the second tray and the second tray is displaced downwardly whereby the stack of sheets fall from the tray and it becomes possible to prevent excessive stacking of sheets whereby the tray can be prevented from being damaged.
Further, in the invention it is preferable that when the second tray is displaced downwardly from the sheet stacking position, the second tray abuts against an image forming apparatus body or a part attached to the image forming apparatus body so that angular displacement of the second tray can be restricted.
Due to such a constitution, since the angular displacement of the second tray is restricted by the image forming apparatus body or the part attached to the image forming apparatus body, it becomes possible to prevent the excessive angular displacement of the second tray so that the second tray can be prevented from being damaged.
Further, in the invention it is preferable that the stopper member is provided with a thin thickness portion to facilitate deformation of the stopper member.
According to the invention, when a load of a stack of sheets exceeding a predetermined load is applied to the second tray, the stopper member is surely deformed and the second tray is surely angularly displaced in the downward direction from the sheet stacking position.
In the invention it is preferable that the thin thickness portion of the stopper member is formed at a proximal end of and at a rear surface side of the sheet tray body where an end portion of the second tray abuts against the stopper member.
According to the invention the second tray can be surely held in the sheet stacking position and the second tray is surely angularly displaced from that position due to the excessive stacking of sheets.
With respect to the above-mentioned second tray, it is needless to say that when the excessive external force is applied to the second tray in the state that the second tray is held at the sheet holding position, the second tray is angularly displaced so that damages of the tray per se due to an excessive external force can be prevented and damages of the supported portion of the second tray can be also prevented.